ignore qmlls versions from 6.8 and below

Now that qmlls is enabled by default, try to disable picking old versions of qmlls (old = 6.8 and below at that point of writing) and use the builtin codemodel instead for a better user experience developing projects on qt version 6.8 an lower.

Why 6.8? The idea is that we can find a fix in 6.8 for the "Qt Language Server" not found issue when the optional "Qt Language Server" package is not installed (see also linked QTBUG-115252 ).